The energy savings on the one hand and the safety standards on the other hand compell the manufacturers of seat articulations for land, aquatic or air vehicles to make assemblies which are more and more compact, light, but yet very resistant so as to provide a great security in all cases; this is the reason why the present invention provides two articulation iron fittings, one with manual control for the locking of the mobile portion on the fixed portion while the other is only a hinge for following the movement but without locking the mobile element with respect to the fixed element.